the Sulphur Moimiam of Ticsan. 119 



extremely full of crevices abound in sulphur*, and exhale a sul- 

 phureous vapour, the temperature of which rose to 47°8 cen- 

 tesimal (118° F.), when the surrounding air was at 20°2(68°F.) 

 Here then is repeated on a small scale, in the clefts of a primitive 

 rock, the phaenomena of the trachytic solfatara of Budoshegy 

 in Transylvania, which has been recently examined by M. 

 Boue. The micaceous schist of Quindiu, which surrounds the 

 open veins^ is decomposed, and the sulphur is formed in masses 

 considerable enough to become the object of a sulphur- work 

 which supports a family settled in the ravine of the Azufral. 

 The rock contains some decomposed pyrites; but I much 

 doubt whether these pyrites perform the important part in 

 nature which has been so long ascribed to them in geological 

 treatises. In the midst of the granitic rocks of Quindiu rise 

 the trachytes of the volcano of Tolima, a truncated cone, which 

 reminds us of the form of the Cotopaxi, and which, according 

 to a geodesic measurement made by me at the west of Ibague, 

 is the highest summit of the Andes in the northern hemi- 

 sphere f. A rivulet which emits considerably the smell of 

 sulphuretted hydrogen descends from the Peak of Tolima, 

 and proves that the trachytes which have penetrated the 

 granitic rocks also contain sulphur. Two learned travellers, 

 MM. Rivero and Boussingault, have recently visited this little 

 solfatara in the micaceous schist of Quindiu : they have sent 

 some specimens to the cabinet of the Ecole des Mines at Paris, 

 which contains the most complete and instructive series of geo- 

 ynostic specimens. Following the Cordillera of the Andes south- 

 wards, these same alternations of primitive formations and of 

 porphyritic and trachytic regions are found : — but what was my 

 surprise, when beyond the equator I ascertained that the cele- 

 brated mountain of sulphur of Ticsan (S. lat. 2" lo'), between 

 Quito and Cuenca, is neither composed of trachyte, nor of 

 chalk or of gypsum, but of micaceous schist. 



This mountain of sulphur, which the Indians call Qiiello, is 

 situated, according to my barometric measurement, at the 

 height of 8000 feet above the level of the ocean. It is entirely 

 composed of primitive micaceous schist { glimmerschiejer^ 

 which is not even anthracitic, as are the varieties of this rock 

 peculiar to transition countries. In some very deep ravines 

 between Ticsan and Alausi, the micaceous schist is seen rest- 

 ing on gneiss. The sulphur is contained in a stratum of quartz 

 which is more than 1200 feet thick: it lies in a tolerably re- 

 gular direction N. 18° E., and inclined like the micaceous 



• See my Barometric and CJcognostic Levelling of the Cordilleras, No. \02. 

 t Height 1H,:521 icct; N. iat. W" 4ti'. 



schist 



